I was recently visiting the web site of the University of London where a "course" (the American definition) is described as a "unit."
So, you take ten units and receive your Masters degree, etc. In Australia (I think it's Australia) a "course" refers to an entire course of study, such as a Bachelors degree program. In South Africa there's a slightly different set of definitions for some of the terms, although I understand that they've made some attempts to "universalize" their nomenclature recently. In short, the definition of the word depends on who is using it. Within the USA I believe there is much consistency, but once you cross those borders you need to double-check.
Jack

3 semesters?

My past studies of Latin tell me there's a misnomer here. Semester includes "semi" meaning "half." Thus, a semester is a term spanning (roughly) half of a year. Can you have 3 halves in a whole? Probably more correct would be "trimester.";)